title: A unique P-glycoprotein interacting agent displays anticancer activity against hepatocellular carcinoma through inhibition of GRP78 and mTOR pathways.
abstract: P-glycoprotein (P-gp) overexpression has been demonstrated in many malignancies being a predominant mechanism by which cancer cells develop multidrug resistance. Several categories of P-gp inhibitors have been demonstrated to potentiate anticancer effect induced by cancer chemotherapeutic drugs through competitive inhibition of P-gp pumping activity. Few studies show the agent that selectively acts on P-gp and, by itself, causes cell apoptosis while remain P-gp-deficient cells unaffected. KNG-I-322, a desmosdumotin B derivative, displayed a direct interaction with P-gp and demonstrated selective anti-proliferative and apoptotic activities in P-gp overexpressed Hep3B/VIN other than P-gp-deficient Hep3B cells. KNG-I-322 induced an inhibitory effect on the phosphorylation of mTOR(Ser2448), p70S6K(Thr389) and 4E-BP(Thr37/46) in Hep3B/VIN but not Hep3B cells. The inhibition was fully blocked by the knockdown of P-gp using siRNA techniques. Notably, the P-gp inhibitor, verapamil, also directly interacted with P-gp but significantly diminished KNG-I-322-induced anti-proliferative activity. After the mechanism study, the data showed that KNG-I-322 induced a dramatic down-regulation of GRP78 expression, which was significantly inhibited by verapamil and completely diminished by the knockdown of P-gp. The protein profile analysis of detergent resistant membranes showed that upon the stimulation by KNG-I-322, the level of P-gp expression in non-raft fractions was dramatically increased and, concomitantly, the GRP78 expression was significantly decreased. Taken together, the data suggest that KNG-I-322 induces anticancer activity in Hep3B/VIN cells through a direct interaction with P-gp, leading to the inhibition of mTOR pathways and the induction of GRP78 down-regulation. The data support that KNG-I-322 is a selective anticancer agent against P-gp-overexpressed other than P-gp-deficient cancer cells.
authors.affiliation: School of Pharmacy, National Taiwan University, No. 1, Sect. 1, Jen-Ai Road, Taipei 100, Taiwan.
authors.forename: Ting-Chun
authors.initials: TC
authors.lastname: Kuo
authors.forename: Po-Cheng
authors.initials: PC
authors.lastname: Chiang
authors.forename: Chia-Chun
authors.initials: CC
authors.lastname: Yu
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nakagawa-Goto
authors.forename: Kenneth F
authors.initials: KF
authors.lastname: Bastow
authors.forename: Kuo-Hsiung
authors.initials: KH
authors.lastname: Lee
authors.forename: Jih-Hwa
authors.initials: JH
authors.lastname: Guh
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects* / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001483:Base Sequence; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D045744:Cell Line, Tumor; D017931:DNA Primers; D004354:Drug Screening Assays, Antitumor; D000091342:Endoplasmic Reticulum Chaperone BiP; D047309:Flavones / Q000494:pharmacology*; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D017931:DNA Primers; D000091342:Endoplasmic Reticulum Chaperone BiP; D047309:Flavones; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C558537:KNI-I-322; D034741:RNA, Small Interfering; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases